Plastics are in common use in a large portion of consumer products. The increased use of plastics is, to a large extent, due to the low cost of plastics in comparison to other materials. In addition, plastics provide durability and strength that are not available from other materials. An inherent property of most plastic materials is that they are not readily biodegradable. This creates a large volume of waste in landfills.
In recent years, there has been increased awareness of the disposal difficulties of plastics and an increased effort to recycle plastic materials. Many plastics are very difficult to recycle into usable materials. Although most thermoplastics can be remelted, the properties of the resulting blend of polymers are difficult to control. The processing properties of most recycled plastics are sufficiently different from the virgin plastic that extruding and molding the recycled plastic is very difficult. In addition, contamination from incompatible plastics and other foreign materials produce inconsistent properties throughout the plastic and a poor quality product. Moreover, contamination can clog conventional plastics processing equipment, thereby making recovery of these materials unpractical.
Recycling of plastics at this time is limited primarily to packaging materials, such as plastic bottles and containers. The recycling of polyethylene terephthalate (PET) has been successful in part due to comparative ease of reclamation and volume of available high quality materials. Other materials which have experienced some success in recycling include high density polyethylene, polypropylene, polyvinyl chloride, polystyrene, polyacrylates, polycarbonates and polyurethanes.
A primary difficulty in recycling many products is the number of different plastics and the varying amounts of plastics in the product. Various processes have been proposed to separate the plastic materials according to type. However, these processes are difficult to control and are typically expensive. In addition, it can be difficult to identify some types of plastics by visual inspection.
Carpeting is one example of a product that usually includes a combination of different polymeric materials. In particular, the carpet fibers are generally different from the materials used for backing. Separating waste carpeting into the respective components is very difficult and generally not economically feasible. Post consumer carpets usually contain large amounts of dirt and other foreign materials which increase the difficulty of recycling. Each year, large volumes of waste carpet are discarded as industrial scrap in the form of trimmings during manufacture or installation as well as post consumer carpet. Regardless of the source, most carpet materials are difficult to recycle.
There has been some effort to recycle various materials that contain filaments or fibers. Examples of processes which use recycled materials are disclosed in U.S. Pat. No. 5,560,797 to Burt et al and U.S. Pat. No. 5,719,198 to Young et al.
Accordingly, there is a continuing need in the industry for processes of recycling various plastic materials and particularly carpeting.